I have a can of tyreweld and a decent 12V compressor in the boot.
At some point I'm going to get a bottle of the tyre sealant that BMW ship in their Mobility Set:
http://www.realoem.com/bmw/showparts...=71&fg=95&hl=1
I have the BMW assist cover as part of the approved-used warranty, but when this expires (assuming I don't renew it) I'll get breakdown cover.
If I had an E9x I'd probably pickup a space-saver off ebay as they seem to be frequently available (unlike the E60).